rpc rewrite: control RPCs using gRPC + separate RPC for data transfer

transport/ssh: update go-netssh to new version
    => supports CloseWrite and Deadlines
    => build: require Go 1.11 (netssh requires it)

transport/local/connect_local.go

@@ -0,0 +1,29 @@
+package local
+
+import (
+	"context"
+	"fmt"
+	"github.com/zrepl/zrepl/config"
+	"github.com/zrepl/zrepl/transport"
+)
+
+type LocalConnecter struct {
+	listenerName string
+	clientIdentity string
+}
+
+func LocalConnecterFromConfig(in *config.LocalConnect) (*LocalConnecter, error) {
+	if in.ClientIdentity == "" {
+		return nil, fmt.Errorf("ClientIdentity must not be empty")
+	}
+	if in.ListenerName == "" {
+		return nil, fmt.Errorf("ListenerName must not be empty")
+	}
+	return &LocalConnecter{listenerName: in.ListenerName, clientIdentity: in.ClientIdentity}, nil
+}
+
+func (c *LocalConnecter) Connect(dialCtx context.Context) (transport.Wire, error) {
+	l := GetLocalListener(c.listenerName)
+	return l.Connect(dialCtx, c.clientIdentity)
+}
+

transport/local/serve_local.go

@@ -0,0 +1,175 @@
+package local
+
+import (
+	"context"
+	"fmt"
+	"github.com/zrepl/zrepl/config"
+	"github.com/zrepl/zrepl/util/socketpair"
+	"net"
+	"sync"
+	"github.com/zrepl/zrepl/transport"
+)
+
+var localListeners struct {
+	m map[string]*LocalListener // listenerName -> listener
+	init sync.Once
+	mtx sync.Mutex
+}
+
+func GetLocalListener(listenerName string) (*LocalListener) {
+
+	localListeners.init.Do(func() {
+		localListeners.m = make(map[string]*LocalListener)
+	})
+
+	localListeners.mtx.Lock()
+	defer localListeners.mtx.Unlock()
+
+	l, ok := localListeners.m[listenerName]
+	if !ok {
+		l = newLocalListener()
+		localListeners.m[listenerName] = l
+	}
+	return l
+
+}
+
+type connectRequest struct {
+	clientIdentity string
+	callback chan connectResult
+}
+
+type connectResult struct {
+	conn transport.Wire
+	err error
+}
+
+type LocalListener struct {
+	connects chan connectRequest
+}
+
+func newLocalListener() *LocalListener {
+	return &LocalListener{
+		connects: make(chan connectRequest),
+	}
+}
+
+// Connect to the LocalListener from a client with identity clientIdentity
+func (l *LocalListener) Connect(dialCtx context.Context, clientIdentity string) (conn transport.Wire, err error) {
+
+	// place request
+	req := connectRequest{
+		clientIdentity: clientIdentity,
+		callback: make(chan connectResult),
+	}
+	select {
+	case l.connects <- req:
+	case <-dialCtx.Done():
+		return nil, dialCtx.Err()
+	}
+
+	// wait for listener response
+	select {
+	case connRes := <- req.callback:
+		conn, err = connRes.conn, connRes.err
+	case <-dialCtx.Done():
+		close(req.callback) // sending to the channel afterwards will panic, the listener has to catch this
+		conn, err = nil, dialCtx.Err()
+	}
+
+	return conn, err
+}
+
+type localAddr struct {
+	S string
+}
+
+func (localAddr) Network() string { return "local" }
+
+func (a localAddr) String() string { return a.S }
+
+func (l *LocalListener) Addr() (net.Addr) { return localAddr{"<listening>"} }
+
+func (l *LocalListener) Accept(ctx context.Context) (*transport.AuthConn, error) {
+	respondToRequest := func(req connectRequest, res connectResult) (err error) {
+		transport.GetLogger(ctx).
+			WithField("res.conn", res.conn).WithField("res.err", res.err).
+			Debug("responding to client request")
+		defer func() {
+			errv := recover()
+			transport.GetLogger(ctx).WithField("recover_err", errv).
+				Debug("panic on send to client callback, likely a legitimate client-side timeout")
+		}()
+		select {
+		case req.callback <- res:
+			err = nil
+		default:
+			err = fmt.Errorf("client-provided callback did block on send")
+		}
+		close(req.callback)
+		return err
+	}
+
+	transport.GetLogger(ctx).Debug("waiting for local client connect requests")
+	var req connectRequest
+	select {
+	case req = <-l.connects:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+
+	transport.GetLogger(ctx).WithField("client_identity", req.clientIdentity).Debug("got connect request")
+	if req.clientIdentity == "" {
+		res := connectResult{nil, fmt.Errorf("client identity must not be empty")}
+		if err := respondToRequest(req, res); err != nil {
+			return nil, err
+		}
+		return nil, fmt.Errorf("client connected with empty client identity")
+	}
+
+	transport.GetLogger(ctx).Debug("creating socketpair")
+	left, right, err := socketpair.SocketPair()
+	if err != nil {
+		res := connectResult{nil, fmt.Errorf("server error: %s", err)}
+		if respErr := respondToRequest(req, res); respErr != nil {
+			// returning the socketpair error properly is more important than the error sent to the client
+			transport.GetLogger(ctx).WithError(respErr).Error("error responding to client")
+		}
+		return nil, err
+	}
+
+	transport.GetLogger(ctx).Debug("responding with left side of socketpair")
+	res := connectResult{left, nil}
+	if err := respondToRequest(req, res); err != nil {
+		transport.GetLogger(ctx).WithError(err).Error("error responding to client")
+		if err := left.Close(); err != nil {
+			transport.GetLogger(ctx).WithError(err).Error("cannot close left side of socketpair")
+		}
+		if err := right.Close(); err != nil {
+			transport.GetLogger(ctx).WithError(err).Error("cannot close right side of socketpair")
+		}
+		return nil, err
+	}
+
+	return transport.NewAuthConn(right, req.clientIdentity), nil
+}
+
+func (l *LocalListener) Close() error {
+	// FIXME: make sure concurrent Accepts return with error, and further Accepts return that error, too
+	// Example impl: for each accept, do context.WithCancel, and store the cancel in a list
+	// When closing, set a member variable to state=closed, make sure accept will exit early
+	// and then call all cancels in the list
+	// The code path from Accept entry over check if state=closed to list entry must be protected by a mutex.
+	return nil
+}
+
+func LocalListenerFactoryFromConfig(g *config.Global, in *config.LocalServe) (transport.AuthenticatedListenerFactory,error) {
+	if in.ListenerName == "" {
+		return nil, fmt.Errorf("ListenerName must not be empty")
+	}
+	listenerName := in.ListenerName
+	lf := func() (transport.AuthenticatedListener,error) {
+		return GetLocalListener(listenerName), nil
+	}
+	return lf, nil
+}